ROTATIONAL MOTION OF METHYLENE CHLORIDE IN A VISCOUS MEDIUM: THE ROTATIONAL CORRELATION FUNCTION OF THE $\nu_{4}$ FUNDAMENTAL ($283 cm^{-1}$) IN POLYSTYRENE-METHYLENE CHLORIDE SOLUTION.

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1967

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Ohio State University

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The time dependence of the rotational correlation function of the vibrational transition moment of the $\nu_{4}$ fundamental of $CH_{2}Cl_{2} (283 cm^{-1})$ between 0 and $1.6 \times 10^{-12}$ sec. has been obtained by the Fourier-inversion of the absorption band about the band center (R. G. Gordon, J. Chem. Phys. 43, 1307(1965) for the pure liquid and for $CH_{2}Cl_{2}$-polystyrene solutions of varying concentrations (molar ratio of $C_{6}H_{5}- CH-CH_{2}/CH_{2}Cl_{2}$ of 0 to 1.5). The decay of the rotational motion of the direction of the transition moment, that is the direction of the $C_{2}$-symmetry axis of the molecule, to Brownian motion is exponential (Markov process) after an initial period of relatively free rotation during the first $0.1-0.2 \times 10^{-12}$ sec. and has dropped to l/e of its initial value after $\sim 0.8 \times 10^{-12}$ sec. The rate of decay is little influenced by the presence of the polymer; this indicates that the component of the rotational diffusion-constant tensor is about the same in the different environments.

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Author Institution: Scientific Laboratory, Ford Motor Company

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